| With the continuous improvement of the railway network,new railways incorporated into the hub process inevitably encounter the problem of roadbed proximity,in order to minimise the interference with the existing roadbed,the use of foam lightweight soil to reduce the impact of the existing roadbed in the process of filling the width of the help becomes a better choice.However,the load transfer mechanism of the foam lightweight soil road base is not yet clear,especially the spatial and temporal deformation characteristics of the structure during operation are not well studied.To this end,a combination of indoor experiments and numerical simulations is used to study the load transfer and spatio-temporal deformation characteristics of the foam lightweight soil proximity roadbed structure for high-speed railways.The main research elements are as follows:(1)Indoor testing of roadbed fillers to obtain the corresponding physical and mechanical parametersPhysical and mechanical tests on loess,graded gravel and Group A and B fillers were carried out by field sampling from a high-speed railway site,and particle analysis tests,compaction tests,straight shear tests and creep tests were conducted on the fillers to obtain parameters such as maximum dry density,angle of internal friction and cohesion of each roadbed filler.Through compression and bending tests,the elastic modulus and flexural strength of different design dry densities of foam lightweight soils were obtained,and the relevant calculation parameters of numerical simulation were obtained.(2)ABAQUS-based simulation model of foam lightweight soil proximity roadbed to study the load transfer characteristics of different structural formsThe ABAQUS numerical simulation software was used to build a simulation model for the proximity roadbed of high-speed railway with foam lightweight soil.Analyse the stress-strain pattern of the roadbed under static load with different widths and filling heights.Study the load transfer characteristics of different gang widths and analyse the variation of the train load influence area with the gang width.To analyse the position of the maximum vertical displacement of the roadbed under different roadbed filling heights and to study the variation of the maximum vertical displacement of the roadbed with the filling height of the roadbed.(3)Numerical simulation analysis of high-speed railway proximity roadbed structure under dynamic train load to study its spatial and temporal deformation characteristicsThe dynamic dynamic train loads are applied to the proximity roadbeds of high-speed railway foam and lightweight soil with different gang widths to analyse their dynamic characteristics and long-term dynamic stability.By comparing the vertical dynamic displacement clouds of different widths of roadbeds,the changes of vertical dynamic displacement and its maximum deformation area under different widths of roadbeds are analysed.The analysis of cyclic loading is carried out to find out the number of loadings when the roadbed reaches a good stability state.(4)To study the effect of different helper filling methods and different parameters of foam and lightweight soil on the additional settlement deformation of existing and new roadbeds,and to propose the recommended structure formBased on the finite element model,the additional settlement deformation of existing and new roadbeds is investigated by using different helper filling methods and different parameters of foam lightweight soil.A comparative analysis of the horizontal and vertical additional deformation of the existing and new road base is carried out for the asymmetric and symmetric fill methods.At the same time,the effect of using different modulus of elasticity and capacity of the foam lightweight soil on the deformation characteristics of the existing-new roadbed is compared and analysed to provide theoretical reference for the selection of a reasonable high-speed railway foam lightweight soil proximity roadbed structure. |
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